This invention relates to a nuclear gyromagnetic resonance apparatus and more specifically to a nuclear gyromagnetic resonance apparatus suited for the measurement of viscosity tensor components of a magnetically anisotropic material.
When a liquid crystal, which is a magnetically anisotropic material, is placed in a magnetic field, molecules of the liquid crystal are oriented in a specific direction which is associated with the direction of the magnetic field. If the relation between the orientation of the molecules and the direction of the magnetic field is compulsively changed under this state, the molecules of the liquid crystal are caused to return to the original direction. By observing the nuclear magnetic resonance spectra of the liquid crystal during this return process, it is possible to measure the viscosity tensor components of the liquid crystal from the spectra. Since the viscosity tensor components are one of the most decisive factors for the response time of the liquid crystal display element, observation on the responsibility of the liquid crystal can be obtained from the viscosity tensor components thus measured.
There are known two methods of changing compulsively the relation between the orientation of the liquid crystal placed in the magnetic field and the direction of the magnetic field; one rotating by a certain angle those magnets which are used for generating the magnetic field and the other rotating by a specific angle a probe placed in the magnetic field together with a sample held by the probe while keeping the magnets stationary. The former is disclosed in "Physics Letters", Volume 36A, No. 3, 30 August, 1971, pp 245-246 and the latter is disclosed in "Solid State Communications", Volume 18, No. 11/12, 1976, pp 1591-1593.
The probe generally includes a fluid path of a heat-insulating structure required for measuring a sample at an optional temperature within a wide temperature range, a thermometer and a magnetic field gradient correcting device for compensating for the inhomogeniety of the magnetic field. Hence, it becomes inevitably large in size. In order to obtain a strong magnetic field using magnets as small as possible, on the other hand, it is necessary to minimize the magnet gaps as small as possible. To satisfy these requirements, it is a customary practice in the art to form the cross-section of the probe in a rectangular shape so that its longer sides are in parallel with the edge face of the magnets while its shorter sides are in parallel with the direction of the magnetic field.
If the magnets or the probe is rotated so as to compulsively change the relation between the orientation of the liquid crystal placed in the magnetic field and the direction of the magnetic field, the gaps between the magnets must be made large so that the magnets must be extremely heavy in weight and extremely large in size.
This problem can be solved to a certain extent by removing from the probe means for setting the sample to an optional temperature and the magnetic field gradient correcting device. In this case, however, it is no longer possible to obtain a nuclear gyromagnetic resonance spectrum having high resolution.